Correlation of in vitro immunological reactions with in vivo tumor immunity: The 125IUdR release cytotoxicity assay and the isotopic antiglobulin technique will be used to study the cell-mediated cytotoxic response and humoral antibody response, respectively, against a Friend virus-induced tumor, FBL-3, in C57BL/6 mice. Tumor transplantation experiments will be used to study the in vivo tumor immunity. Correlation of humoral antibody response to primary chemical and virus induced tumors. Correlation of generation of cytotoxic lymphocytes in vitro against syngeneic tumor cells, particularly FBL-3 cells.